1. Field of the Invention
The present invention relates to a semiconductor apparatus, and in particular, to a semiconductor apparatus in which a semiconductor device and a wiring member having an insulating resin base, wiring layers connected to the individual electrodes of the semiconductor device, and external terminals, are bonded to each other with an insulating elastic material therebetween, and to an electronic system using such a semiconductor apparatus.
2. Description of the Related Art
In a semiconductor apparatus such as an apparatus of a chip size package (CSP) type, each electrode of the semiconductor device is extracted through a wiring member. The wiring member for extracting electrodes includes a base composed of an insulating resin such as polyimide, and wiring layers composed of, for example, copper. One end of each wiring layer is, for example, directly connected to each electrode of the semiconductor device, and the other end is provided with an electrode (e.g., a ball-shaped electrode composed of solder) as an external electrode. The wiring member and the semiconductor device are bonded to each other.
With respect to a semiconductor apparatus in which electrodes of a semiconductor are extracted through the wiring member as described above, Japanese Patent Publication No. 6-504408 discloses that the connection between a wiring member and a semiconductor device is performed by interposing an insulating elastic material. In a semiconductor apparatus, in response to changes in temperature during use, a relative movement occurs between a wiring member and a semiconductor device because of the difference in coefficient of thermal expansion between the two, and the relative movement may exert a force between the individual electrodes of the semiconductor device and the electrodes of the wiring member, resulting in an increase in strain, fracturing of electrodes, and the like.
In accordance with the patent publication described above, the insulating elastic material enables the wiring member to move in relation to the semiconductor device, and the insulating elastic material has an indentation hardness of approximately 20 to 70.
However, the present inventors have found, by testing, that the technique disclosed in the above-mentioned patent publication is not practical. Although in this technique it is generally understood that a material is used which is elastic at temperatures higher than room temperature, rubber elasticity is not always retained under the environmental conditions of the fabrication process and of use by being elastic only at temperatures higher than room temperature, and at low temperatures, for example, at xe2x88x9255xc2x0 C., the required effect cannot be expected.
Generally, a rubber elastic material has rubber elasticity at temperatures higher than a glass transition temperature, and loses elasticity at temperatures lower than the glass transition temperature because the material is transformed into a glassy state. FIG. 10 is a graph which shows the dependence of the relative Young""s modulus and loss modulus on temperature with respect to styrene-butadiene rubber as a general rubber. Specifically, FREQUENCY at an axis of ordinates corresponds to Young""s modulus (elastic modulus), and DAMPING at the other axis of ordinates corresponds to loss modulus. In the drawing, the solid line shows a change in Young""s modulus by temperature, and the dashed line shows a change in loss modulus by temperature. As shown in the graph, the rubber has a glass transition temperature of xe2x88x9237xc2x0 C., and at temperatures lower than that, the rubber is transformed into a glassy state and loses rubber elasticity.
Semiconductor apparatuses are required to be operated, generally, at xe2x88x9255xc2x0 C. to 125xc2x0 C., or, at a higher level, at xe2x88x9255xc2x0 C. to 150xc2x0 C. Therefore, when a general rubber is used as an insulating elastic material between wiring members and semiconductor devices, it loses rubber elasticity at xe2x88x9235xc2x0 C. or less, and thus the requirement cannot be satisfied. The above-mentioned patent publication does not describe the need for such a requirement to be met, or the specific means to satisfy the requirement.
Accordingly, the present invention has been made to satisfy the requirement described above. With respect to a semiconductor apparatus in which a semiconductor device and a wiring member having an insulating resin base, wiring layers connected to the individual electrodes of the semiconductor device, and external terminals, are bonded to each other with an insulating elastic material therebetween, it is an object of the present invention to prevent the insulating elastic material from losing rubber elasticity at low temperatures, and thus, to enhance the reliability of the semiconductor apparatus and also the reliability of an electronic system using the semiconductor apparatus.
In one aspect, in accordance with the present invention, a semiconductor apparatus includes an insulating elastic material that retains rubber elasticity under the environmental conditions of the fabrication process and of use.
In the semiconductor apparatus of the present invention, since the insulating elastic material always retains rubber elasticity, the relative movement between the wiring member and the semiconductor device in response to changes in temperature is always allowed. Therefore, an increase in strain or fracturing can be prevented in the semiconductor device, particularly around the electrodes, resulting from the incapability for relative movement between the wiring member and the semiconductor device because of the loss of rubber elasticity by the insulating elastic material, and thus low-temperature resistance and reliability of the semiconductor apparatus can be improved.
Preferably, the insulating elastic material has rubber elasticity at xe2x88x9250 to 120xc2x0 C.
In another aspect, in accordance with the present invention, an electronic system includes at least a semiconductor apparatus in which a semiconductor device and a wiring member having an insulating resin base, wiring layers connected to the individual electrodes of the semiconductor device, and external terminals, are bonded to each other with an insulating elastic material therebetween, and the insulating elastic material retains rubber elasticity under the environmental conditions of the fabrication process and of use.
Accordingly, in the electronic system of the present invention, since the semiconductor apparatus, in which the insulating elastic material always retains rubber elasticity to allow the relative movement between the wiring member and the semiconductor device in response to changes in temperature, is used, low-temperature resistance and reliability of the electronic system can be improved.
Preferably, the insulating material has rubber elasticity at xe2x88x9250 to 120xc2x0 C.